Field of the Invention
The present invention relates to wireless communications, and more particularly, to method and device for performing ranging for Machine To Machine (M2M) communication.
Related Art
Machine To Machine (M2M) communication is one type of data communication including one or more entities not requiring human interactions. M2M communication may also be called as Machine Type Communication (MTC). That is, the M2M communication refers to the concept of communication based on the existing wireless communication network used by a machine device that is not directly operated by a human. The machine device used in the M2M communication can be called a M2M device. There are various M2M devices such as a vending machine, a machine of measuring a water level at a dam, etc.
The M2M device has a feature different from that of a typical human-operated device. Therefore, a service optimized to the M2M communication may differ from a service optimized to human-to-human communication. In comparison with a conventional mobile network communication service, the M2M communication can be characterized as a different market scenario, data communication, less costs and efforts, a potentially great number of M2M devices, wide service areas, low traffic for each M2M device, etc.
Ranging is a procedure used to initiate or keep uplink synchronization. There are two types of ranging: initial ranging and periodic ranging. After downlink synchronization, the mobile station attempts to perform initial ranging with a base station. If the ranging procedure is successfully completed, the mobile station is uplink synchronized with the base station. Periodic ranging is the process of maintaining the correct mobile station's uplink transmission parameters.
Ranging is generally a contention based ranging in which collisions between mobile stations occur. For exampling, it is assumed that two mobile stations transmits same ranging codes via same ranging channels. The base station cannot receive all ranging codes or can receive only one ranging code. This means that one or more mobile stations re-transmits another ranging code after random backoff. The collision may occur when mobile stations performs ranging simultaneously.
To reduce possibility of collision in the contention based ranging, allocation of dedicated ranging channel has been proposed.
However, it is required to consider the M2M communication feature to perform ranging using the dedicated ranging channel.